A small magnetic disk drive of the prior art is described in unexamined Japanese patent publication 6-96532. According to this publication, stacked recording disks are rotated with a constant velocity by a disk rotating motor which is fixed to a base. Heads are supported by supporting springs to a carriage, and float on the disks with a minute gap, and record and reproduce information. A voice coil motor rotatively drives the carriage and precisely positions the heads with high speed. The carriage is supported to a pivot assembly consisting of a sleeve with a shaft and two ball bearings and is fixed to the base, so that the carriage can rotate around the shaft.
The voice coil motor which drives the carriage includes a driving coil, permanent magnet, and yoke. The driving coil is fixed to the carriage and the permanent magnet and yoke (referred to as "magnet yoke assembly") are fixed to the base. The driving coil is placed in a magnetic field and magnetically affected so that with an electric current flowing through the driving coil drives the carriage to position the heads as desired.
Recently, such devices are becoming smaller and thinner and the market for removable and portable pocket-sized devices like IC cards is growing. Therefore, a durable device is required to bear the shock and prevent any damage from occurring to the device even when it is bumped or dropped to the floor. There are two ways to improve the durability. One is to improve the durability of each individual element inside the device such as positioning mechanism, disks, and slider, etc. Another way is to protect the whole device from shock.
An example of protecting the whole device from shock is disclosed in unexamined Japanese patent publication 1-311495. In this example, vibration and shock-absorbing materials are arranged on all four sides of the device and the device body is mounted to the inner case by the vibration and shock-absorbing materials. The inner case is provided with projected guides and is removably stored in a case having a guide rail. This way, the vibration and shock transmitted to the device body is reduced.
Another example is disclosed in unexamined Japanese patent publication 4-368690. In this example, chloroprene rubber shock-absorbing materials are arranged at the four corners of the magnetic disk drive housing, thereby protecting the inner mechanism of the device from damage.